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Electronic Subscriber Set With Improved Flashing Disclosure Number: IPCOM000048213D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08

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Diehl, V Wolf, S [+details]


The figure is a schematic of the circuit for a telephone subscriber set using a considerable number of electronic components. Multi-frequency (MF) dialing is controlled by 12 dialing keys, and there are 10 service keys for dial repetition, three party conference, short dialing, etc. To prevent disturbances in the earphone when a key is activated, transistor T1, which is part of a side tone protection circuit, is cut off. Activation of any one of the 22 keys causes a signal to be stored in an MF coder and a storage unit. Hence, only one electrical contact need be provided for the keys. The MF coder controls an MF generator, by means of which a multi-frequency signal is applied to the subscriber line.